Greetings,

I'm in the middle of another rebuild and had some pictures on hand, so just thought I'd share in case it helps someone down the road.

When I do EMs, my preference is to do a 'bottoms up' rebuild, rather than a 'top down, get it to work' approach. As part of that, I start with the base cabinet, completely stripped of hardware, and start systematically going through everything, rebuilding it as I go. Here's one that's already been partially rebuilt:

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The score motor board is over on the bench, and everything’s been stripped off that too:

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Besides going through all the relays and such, the main event of rebuilding the score motor board is the score motor itself. Since the score motor board sits on the bottom of the cabinet, all the gunk through the years lands there, making for a general mess, and the score motor is a key component of the game operating well. So I like to take it all apart as well, and give it a thorough detailing.

The first step is taking pictures of all the switch stacks. Despite having done dozens of these, it’s still easy to get switch stacks mixed up, especially after they’re off and loose. So side pictures and top pictures are cheap insurance. And if you’re not able to complete the project in one setting, it helps for coming back to it later.

As these example pictures show, this particular score motor has dried gunk on it, as well as the crusty, powdery debris that likes to build up. That all needs to get cleaned up. But this one isn’t too bad really; they can be much, much worse.

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During this process I’m also looking at the switches, keeping an eye out for loose wires and incorrectly gapped blades. This one had a whole switch stack that was bent up too far:

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But I address those later during reassembly.

To take it apart, I start at the #3 position and remove the switch stack, then work counter clockwise to remove the rest of the switch stacks. (I also take the brake switch off.) Note the positions of the ‘switch dog’ brackets (the brackets that look a bit like flat tuning forks). Also note the slots that the switch dogs are in (these are the little black lifter arms). (If you forget, the only switch dog that’s in the ‘L’ slot is the one on #2; the rest are always in the ‘S’ slot.)

I tend to keep the bolts in the switch spacers, but they can fall out that way. You can slip little plastic baggies over each stack and place a rubber band around them to keep them all together though (or whatever method works well for you).

Note switch stacks that span either side of the mounting post too.

Also pay attention to switch stacks that are ‘tied’ together through a solder bridge or short bridge wire. These are a pain to remove, so take your time. If the solder bridge breaks, no big deal, just resolder it after reassembly.

Once the switch stacks are all removed, then the motor cam can be removed. It’s held in place with a set screw on the shaft. If you’re lucky, it will just slide up and slip off. But they are often frozen, caught in place by a burr raised by the set screw. To get the stubborn ones off, I wrap a bit of cloth around the portion of the shaft that sits below the motor gears and then hold it with pliers while I work the motor cam back and forth until it’s able to slide off. It can take while, but they’ve all come off eventually. (To avoid this issue in the future, I then file down the burr on the shaft.)

After the motor cam is off, then I remove the mounting bracket from the motor assembly. This is held in place with three screws.

The neat thing about the later Gottliebs is that they hand wrote a build date on the top of the score motor with a Sharpie. So one reward in doing this is being able to see that date:

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This particular motor assembly has a manufacturing date stamped on the metal of “5 78”, but as can be seen, it has a handwritten date of 8-17-78, which indicates when this game was being assembled. Cool beans.

So that was the tear down. Now all the parts are cleaned. I clean and polish the motor cam, mounting bracket, switch dog brackets and switch dogs, and degrease and clean the switch blades (especially the ones that have prongs coming into contact with the motor cam; they like to accumulate dried grease on them). I burnish all the switch contacts too (they’re easier to access at this point).

The metal parts do clean up nicely:

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If you’re working on a 60’s Gottlieb that has the phosphorous bronze plated metal parts (brass or gold colored), then a citrus degreaser called Zep (available at Home Depot) followed by some Mother’s Mag&Aluminum polish really puts a shine on that type of part. (And I mean sunglass-inducing shine.)

I put a drop of machine oil on the oiling pad underneath the motor (where the hole in the metal plate is). The motor needs to be flipped over for this, and sit level. The mounting bracket flipped upside down makes a great trivet that works for this. I also use a Q-tip (wetted with a solvent or alcohol) and clean around the gears and the lower part of the motor assembly where dust and gunk accumulates, but I don’t put any oil or lubricant on any other part of the motor.

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After the cleaning is complete and all the switches have been gone through, then it’s time for reassembly. Basically it’s just reversing the steps. Mounting bracket back on, motor cam back on, switch stacks back on (but starting at position 4 and working clockwise now).

I put a dab of SuperLube on the switch dogs and on the switch blades that contact the motor cam. The score motor gets a lot of workout, and the metal on metal contact is helped that way.

While I’m putting the switch stacks back on, I check each stack as I go by manually rotating the motor cam, to make sure the contacts are working correctly and making any adjustments. This is the time to really get this right, since after the board goes back into the game, it’s very, very difficult to work on. I adjust any switch stacks as needed, and resolder anything as needed. I don’t want to have to revisit the score motor ever again after this. 

Once it’s all put back together, I reassemble the board and put the board back into the cabinet. I also clean and polish the fillister head bolts and their washers that hold the board in place, for a little added bling.

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It takes me around 90 minutes to do a score motor like this, sometimes more if there are several issues to address. The neat thing is that Gottlieb used pretty much this same setup on games going back to at least the late 1940’s, and while some of the materials and platings changed, the process doesn’t change much (other than adjusting to clean the different types of material). The older games have the score motor bolted directly to the board, while the later ones have an intermediate bracket/stand that allow the score motor to be flipped up.

Good luck!

True, some metal seems to 'stain' based on whatever gunk sat on it for years. I start with least aggressive and work up as needed. My 'go to' is a quick dip in diluted CLR followed up with a polish using Mother's Mag & Aluminum polish. This stuff has cut my time way, way down. Unless it's the phosphorous bronze plated metal, then I use Zep instead. If the metal is rusty, I use Oxalic acid (because I have a supply; Evap-o-rust would probably work too), followed by steel wool, and then Mother's. And if that's not enough, than I'll resort to something mechanical, like a wire wheel or other abrasive. But that's rare. I don't like using a mechanical solution to a chemically caused problem, if I can avoid it. I try to 'undo' the problem with other chemicals first if possible. But then a nice polish and buffing is 'mechanical' too I suppose. At least this is what's worked best for me; undoubtedly there are other approaches, and some folks may have better luck going straight to buffing (for example). I love hearing about new techniques to try though.

Good question!